Thanks for reply, well technically what i want to do is not a chart, its more like a file editor, but more advanced.
Let me be more explicit about what i want here:
i have an array of word.
I display it as shown above.
Maybe to you the lines on the screen doesn't tell you much, but for me (as i was trained to work with similar file editing software) tells me a lot.
When i see the part im interested in, i want to select it, so the selection should give me the begin-end address of the data from array.
The so called "vertical cursor", i want a line from top to bottom to act as a cursor, to be able to move it around the screen, where its position will be the position from array.

And about the grid lines you give me in idea:
Instead of clearing bp , i will clear it and draw the grid at the same time, then will draw my data on it. Hows that sounds?